Mass spectrometers are well known and are used in the analysis of a wide array of substances. The use and effectiveness of the mass spectrometers can be enhanced by providing a variety of optional support equipment. One such useful optional support equipment is an automatic sample loader or autosampler. Typically these are intended for the analysis of biochemical samples. One example of such a product is the Surveyor Autosampler™ from Thermo Finnigan. Although the design and capabilities of commercial autosamplers vary, they are, in general, effective in automatically loading liquid samples from a variety of containers, including source plates, vials, test tubes, etc. However, the methods these autosamplers use to handle sample material are not suitable for very low volume (typically below 20 μl) biological samples. Typically, a commercial autosampler first aspires the sample from its container and injects it into the sample loop of a specialized injection valve, when the valve is in load position. The valve is then switched to inject position and a metering pump pumps buffer to flush the sample from the sample loop through interconnecting tubing and into the mass spectrometer column.
Although this process works well for larger, chemical samples, it is not considered satisfactory for small biological samples for a number of reasons. For example a large part of the sample, sometimes as much as fifty percent (50%) is lost in the process due primarily to large dead volume (typically about 40 μl) on the intake side of the sample loop. As well this process is not desirable for small biological samples because the sample comes in contact with relatively large surfaces of conduits on its way from the container to the column and inevitably, some of the molecules attach to the walls, which leads to further loss of sample material and cross-contamination as the leftover material mixes with the newly transferred sample in the following cycle. Further the sample is diluted by the buffer, which requires larger volumes of the mixture to be pumped through the column.
As a result of these shortcomings small biological samples need to be loaded to the mass spectrometer column manually. This requires lab personnel to continuously attend to the operation of the instrument.
Accordingly it would be desirable to provide an autosampler that may be used with small biological samples.